public class Test1 {
     private static int count = 0 ;
    public static void main(String[] args) throws InterruptedException {
        Object locker = new Object() ;
        Thread t1 = new Thread(()->{
            for (int i = 0; i < 50000; i++) {
                synchronized(locker){
                    count ++ ;
                }
            }
        });
        Thread t2 = new Thread  (()->{
            for (int i = 0; i < 50000; i++) {
                synchronized(locker){
                    count ++ ;
                }
            }
        });

        t1.start();

        t2.start();
        t2.join();
        t1.join();
        System.out.println("count:" +count);

    }
}
